Lankenau Heart Institute

Myocardial Perfusion Scan, Resting

A myocardial perfusion scan is a type of nuclear medicine procedure.
This means that a tiny amount of a radioactive substance, called a
radionuclide (radiopharmaceutical or radioactive tracer), is used during
the procedure to assist in the examination of the tissue under study.
Specifically, the myocardial perfusion scan evaluates the heart's
function and blood flow.

A radionuclide is a radioactive substance used as a "tracer," which
means it travels through the blood stream and is taken up (absorbed) by
the healthy heart muscle tissue. On the scan, the areas where the
radionuclide has been absorbed will show up differently than the areas
that do not absorb it (due to possible damage to the tissue from
decreased or blocked blood flow).

A resting myocardial perfusion scan is used to assess the blood flow to
the heart muscle (myocardium) and to determine what areas of the
myocardium have decreased blood flow. This is done by injecting a
radionuclide (thallium or technetium) into a vein in the arm or hand.

There are different types of radionuclides. When one type of
radionuclide is used, areas of the myocardium that have blocked or
partially blocked arteries will be seen on the scan as "cold spots," or
"defects," because these areas will be unable to take in the
radionuclide into the myocardium. Another type of radionuclide binds to
the calcium that is released when a heart attack occurs, so it will
accumulate in area(s) of injured heart tissue as a "hot spot" on the
scan.

Coronary
artery disease (CAD) is the narrowing of the coronary arteries (the
blood vessels that supply oxygen and nutrients to the heart muscle),
caused by a buildup of fatty material within the walls of the arteries.
This process causes the inside of the arteries to become rough and
narrowed, limiting the supply of oxygen-rich blood to the heart muscle.

To better understand how coronary artery disease affects the heart, a
review of basic heart anatomy and function follows.

The heart is basically a pump. The heart is made up of specialized
muscle tissue, called the myocardium. The heart's primary function is to
pump blood throughout the body, so that the body's tissues can receive
oxygen and nutrients and have waste substances taken away.

Like any pump, the heart requires fuel in order to work. The myocardium
requires oxygen and nutrients, just like any other tissue in the body.
However, the blood that passes through the heart's chambers is only
passing through on its trip to the rest of the body. This blood does not
give oxygen and nutrients to the myocardium. The myocardium receives its
oxygen and nutrients from the coronary arteries, which lie on the
outside of the heart.

When
the heart tissue does not receive an adequate blood supply, it cannot
function as well as it should. If the myocardium's blood supply is
decreased for a length of time, a condition called ischemia may develop.
Ischemia can decrease the heart's pumping ability, because the heart
muscle is weakened due to a lack of food and oxygen.

Fortunately, the technology is available to restore blood flow to heart
tissue when coronary artery blockages are diagnosed. One of several
procedures used to diagnose and evaluate coronary artery disease is the
resting myocardial perfusion scan.

Possible indications for a resting myocardial perfusion scan may
include, but are not limited to, the following:

Chest pain, either new onset or occurring over a period of days
or longer

Following a heart attack (myocardial infarction, or MI)

To assess blood flow to areas of the myocardium that have been
reperfused (coronary artery blood flow restored) by bypass
surgery, angioplasty (the opening of a coronary artery using a
balloon or other method), or stent (a tiny expandable metal coil
placed inside the artery to keep the artery open

The injection of the radionuclide may cause some slight discomfort.
Allergic reactions to the radionuclide are rare.

If you are pregnant or suspect that you may be pregnant, you should
notify your health care provider due to the risk of injury to the fetus
from myocardial perfusion scan. If you are lactating, breastfeeding, you
should notify your health care provider due to the risk of contaminating
breast milk with radionuclide. Radiation exposure during pregnancy may
lead to birth defects.

Patients who are allergic to or sensitive to medications, contrast dye,
iodine, tape, or latex should notify their doctor.

There may be other risks depending on your specific medical condition.
Be sure to discuss any concerns with your doctor prior to the procedure.

Certain factors or conditions may interfere with or affect the results
of the test. These include, but are not limited to, the following:

Caffeine within 24 hours of the procedure

Digitalis, quinidine, or nitrate medications

Your doctor will explain the procedure to you and offer you the
opportunity to ask any questions that you might have about the
procedure

You will be asked to sign a consent form that gives your
permission to do the test. Read the form carefully and ask
questions if something is not clear

Notify your doctor if you are allergic to or sensitive to
medications, local anesthesia, contrast dyes, iodine, tape, or
latex

Fasting may be required before the procedure. Your doctor will
give you instructions as to how long you should withhold food
and/or liquids. You should refrain from eating or drinking
anything that contains caffeine for at least 24 hours prior to
the procedure. Some prescription and over-the-counter
medications contain caffeine and should be avoided. Some
over-the-counter medications that contain caffeine include
Anacin, Excedrin, and NoDoz

Notify your doctor of all medications (prescription and
over-the-counter) and herbal supplements that you are taking

If you are pregnant or suspect that you may be pregnant, you
should notify your doctor

Notify your doctor if you have a pacemaker

Based on your medical condition, your doctor may request other
specific preparation

A resting myocardial perfusion scan may be performed on an outpatient
basis or as part of your stay in a hospital. Procedures may vary
depending on your condition and your doctor's practices.

Generally, a resting myocardial perfusion scan follows this process:

You will be asked to remove any jewelry or other objects that
may interfere with the procedure.

You will be asked to remove clothing and will be given a gown to
wear.

An intravenous (IV) line will be started in your hand or arm.

You will be connected to an ECG machine with leads and a blood
pressure cuff will be placed on your arm.

You will lie flat on a table in the procedure room.

The radionuclide will be injected into a vein in your arm or
hand.

After the medication has circulated through your body (10 to 60
minutes depending on the radioactive tracer being used), the
scanner will begin to take pictures of your heart. In a special
kind of imaging test, called SPECT (single photon emission
computed tomography), the scanner will rotate around you as it
takes pictures.

You will be lying flat on a table while the images of your heart
are obtained. Your arms will be positioned on a pillow above
your head. It will be necessary for you to lie very still while
the images are being taken, as movement can adversely affect the
quality of the images.

If you experience any symptoms, such as dizziness, chest pain,
extreme shortness of breath, or severe fatigue, at any point
during the procedure, let the doctor or technologist know.

After the scan is complete, the IV line will be discontinued,
and you will be allowed to leave, unless your doctor instructs
you differently.

You should move slowly when getting up from the scanner table to avoid
any dizziness or lightheadedness from lying flat for the length of the
procedure.

You will be instructed to drink plenty of fluids and empty your bladder
frequently for 24 to 48 hours after the test to help flush the remaining
radionuclide from your body.

The IV site will be checked for any signs of redness or swelling. If you
notice any pain, redness, and/or swelling at the IV site after you
return home following your procedure, you should notify your doctor as
this may indicate an infection or other type of reaction.

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